Flow cytometric assessment of allopurinol susceptibility in Leishmania infantum promastigote.

Background: Leishmaniasis is a major tropical and subtropical parasitic disease. Sodium stibogluconate, N-methyl -D-glucamine antimoniate, amphotericin B, pentamidine, and ketoconazole are drugs used to treat this disease. Some of these drugs cause severe adverse side effects and treatment failures are common. Allopurinol, a purine analog, has been used to treat leishmaniasis, alone or combined with the previously mentioned drugs. Low cost, ease of administration (oral), and lack of toxicity make allopurinol a particularly appealing candidate.

Methods: The effect of allopurinol on Leishmania infantum (MCAN/ES/89/IPZ229/1/89, zymodeme MON1) wild-type promastigotes (wt-p229), and an altered form of these promastigotes (allo-p229) resulting from long term in vitro exposure to allopurinol, was determined by [(3)H]-thymidine incorporation assays and by diverse flow cytometric approaches.

Results: Allopurinol arrested the proliferative capacity of wt-p229 promastigotes, reduced the proportion of viable cells, and decreased their total protein content. In contrast, allo-p229 promastigote proliferation was only slightly decelerated and the proportion of viable cells and the protein content were not affected by the allopurinol treatment.

Conclusions: The flow cytometry approach allowed us to demonstrate differences in allopurinol susceptibility of the two promastigote forms, expanding the spectrum of flow cytometry applications in studies of parasite resistance.